Spark plug



May 20, 1952 L. M. FIELD 2,597,718

V i Jj] INVENTOR. Zogdjlz Zd May 20, 1952 1 M. FIELD 2,597,718

SPARK PLUG Filed oct. 17, 1949 2 SHEETS-SHEET 2 IN VEN TOR.

Patented May 20, V1952 UNITED smrss FFECE SPARK PLUG Application October 17, 1949, Serial No. 121,763

the general custom to discard the entire plug because the points had spent their usefulness, the plug shell and porcelain being otherwise in serviceable condition. It was also brought out in the identified patent that the principal wear on a spark plug was in the negative electrode and in said patent provision was made for a replaceable negative electrode so that the life of a spark plug could be extended beyond the life of the electrode.

It is therefore the primary object of the present invention to improve the type of negative electrode and in a way to facilitate proper placement of a substitute negative electrode on the threaded stem of the spark plug.

'I'he negative electrode is of generally U-shape and the legs of the electrode are threaded at their outer sides and said legs are receivable in longitudinal grooves formed in diametrically opposite sides of the threaded stem ofthe spark plug body. It is essential that the threads on the legs of the U-shaped negative electrode perfectly mate with threads on the stem of the spark plug body and 'to accomplish` this result one of the legs of the negative electrode is longer than the other leg, providing a long and short leg receivable in relatively long and short mating grooves in the threaded stem of the spark plug and a structure o this character facilitates assembly of the substitute negative electrode on the spark plugs, with the assurance that the threads on the legs of the electrode will properly mate with the threads of the spark plug stem for perfect entry into a threaded port in an engine cylinder.

It .is a further object of the invention to improve the center positive electrode and in one formy of the invention the insulating core or porcelain body of the electrode mounted within the metallic shell or body includes an elongated tubular portion and a iioating tip at the lower end of the spark plug that normally extends below the porcelain and is movable between the fixed tubular electrode section and the cross b ar or arm of the U-shaped negative electrode.

Astill further object of the invention is to provide a spark plug of the foregoing character wherein the insulating core or porcelain has an annular chamber at its lower end so that the floating tip of the center positive electrode will seat on a shoulder of the porcelain body at the upper end of the chamber and also on the lower end of the tubular center electrode to provide a double seal.

A further object of the invention is to provide a spark plug embodying a replaceable U-shaped negative electrode mounted on the threaded stem of the spark plug body or casing and a tubular center positive electrode with a oating tip having an enlarged lower end freely mounted in a chamber at the lower end of the insulating core or porcelain body with a stem of reduced diameter extending upwardly from the floating tip with the upper end of the stem engageable with the lower end of a xed center tubular electrode section, while the enlarged lower end of the tip moves into engagement with a shoulder at the upper end of the chamber in the lower end of the porcelain;

It is a further object of the invention to provide a replaceable U-shaped negative electrode in which the legs thereof extend the entire length of the threaded stem of the spark plug body and of such'length for reception in sockets or recesses in the lower end of the body or casing upwardly of the threaded stem portion thereof or to be bent outwardly for reception in grooves extending transversely of the lower end of the spark plug body or casing at the upper end of the threaded stem portion thereof.

It is known that repeated ring of a spark plug results in intense heating of the negative electrode and it is an important object of this invention to dissipate such heat as rapidly as possible, and such action is caused by placing the legs of the negative electrode into direct contact with the threaded port of an engine cylinder so that such excessive heat is dissipated into the Water jacket or cooling system.

With the above and other 'objects in View that will become apparent as the nature of the invention is better understood, the same consists in the novel form, combination and arrangement of parts hereinafter more fully described, shown in the accompanying drawings, and claimed.

In the accompanying drawings:

Figure 1 is a side elevational view of a spark plug constructed in accordance with the present invention,

Figure 2 is a sectional view taken on line 2--2 of Figure 1, which shows a portion of the negative electrode extending across the end of the park plug and in position for contact by the center positive electrode,

Figure 3 is a fragmentary elevational view of the lower threaded end of the spark plug with the negative electrode in position to be assembled therewith and showing a side slot in the threaded stem of the plug to receive a side leg of the U-shaped negative electrode, the side walls of the slot being slightly tapered to provide frictional contact between the electrode and plug and a binding retaining activity,

Figure 4 is a fragmentary side elevational View, partly in section, of a spark plug constructed in accordance with the present invention, showing the legs of the U-shaped negative electrode and the grooves in the threaded stem of the spark plug being of different lengths to facilitate mating of threads on the legs of the electrode with the threads of the spark plug stem and also showing the floating tip of the positive electrode moving between the negative electrode and a fixed tubular section of the center positive electrode,

Figure 5 is a fragmentary side elevational View partly in section, similar to Figure 4, but showing a modified form of the invention wherein an enlarged annular chamber is formed at the inner end of the insulating core or porcelain with an abutment shoulder at the upper end of the chamber, while the floating tip is proportioned for engagement with both the shoulder and the lower end of the center tubular electrode,

Figure 6 is an enlarged fragmentary sectional View of the lower end of the porcelain and center electrode sections shown in Figure 5 to illustrate the engagement between th floating tip and center electrode and also the shoulder at the upper end of the enlarged chamber at the lower end of the porcelain,

Figure 7 is a fragmentary side elevational view, partly in section, similar to Figure 5, with the xed tubular center electrode terminating at its lower end above the enlarged chamber at the lower end of the porcelain and engaged by an extension stem on the floating tip of the center electrode,

Figure 8 is a fragmentary side elevational view. partly in section, of another form of U-shaped negative electrode with the side legs thereof of a length extending the full length of the threaded stem of the spark plug casing and with the ends of the legs received into sockets in the base of the spark plug body,

Figure 9 is a cross-sectional View taken on line 9-9 of Figure 8,

Figure 10 is a fragmentary side elevational View, partly in section, of the form of invention shown in Figure 8, and illustrating a spark plug with its U-shaped negative electrode mounted in the threaded port of an engine cylinder with the threads in the cylinder port biting into the legs of the negative electrode to facilitate the dissipation of heat, and

Figure 1l is a fragmentary side elevational view, partly in section, of another form of spark plug wherein the U-shaped negative electrode has the terminal ends of its side legs bent outwardly for reception in grooves at the base of the spark plug body and underlying the usual sealing gasket.

Referring more in detail to the accompanying drawings and particularly to Figures 1 to 4 thereof, there is illustrated a spark plug comprising an insulating core or porcelain I5 mounted within a shell or body I6, the latter carrying the threaded stem l1 for mounting in a port in an engine 4 cylinder. As shown in Figure l, there is a center positive electrode designated in general by the reference character I8, a U-shaped negative electrode I9 extending across the lower open end of the threaded stem Il, while a cap nut 2i) or the like at the upper end of the plug retains a conductor in engagement with the center electrode.

As illustrated in Figure 4, the lower end of the body or shell I6 is shouldered as at 2l and the threaded stem Il depends centrally therefrom. The porcelain I5 has a central bore for the mounting of the stationary or fixed tubular section 22 of the center positive electrode I8 and this tubular section 22 terminates at its upper end above the lower end of the porcelain I5 for the reception of the floating tip 23 forming a part of the center positive electrode.

The threaded stem I1 of the spark plug is longitudinally grooved at its outer side at diametrically opposite points providing a relatively long groove 24 and a relatively short groove 25, the grooves while being of different lengths, both terminate in spaced relation to the shoulder 2| of the body or shell I6. A U-shaped negative electrode as generally indicated at I9 includes a relatively long side leg 26 and a relatively short side leg 21 for respective reception in the relatively long and short grooves 24 and 25 in the threaded stem I1. The cross arm 28 of the U- shaped negative electrode is preferably provided with an upstanding center hump 29 in line with the floating tip 23 of the center positive electrode. As illustrated, the outer sides of the legs 26 and 2l of the negative electrode are threaded as at 39 and these threads mate with the threads on the stem Il' of the spark plug casing, and to make sure that the legs of the negative electrode are positively seated in the grooves with the threads thereof mating with the threads of the spark plug stem, the side walls of the grooves 24 and 25 are slightly tapered as shown in Figure 3 by the reference character 3| so that a slight percussive force applied to the cross arm of a U-shaped negative electrode will effect proper seating thereof for the mating of the threads and such frictional seating will permit easy handling of the plug after placement of the negative electrode without liability of the negative electrode becoming accidentally disengaged from the spark plug.

In the manufacture of spark plugs described herein, the legs of the U-shaped negative electrode may be pre-threaded if desired or they may be nished in blank and threaded when applied to a spark plug. It will be understood that the usual gasket is interposed between the shoulder 2l of the spark plug casing and an engine cylinder and there is direct contact between the legs of the U-shaped negative electrode and the engine cylinder with its associated water jacket for the rapid dissipation of heat built up in the negative electrode. It is also important that the legs of the electrode be of different lengths to accomplish proper mating of the threads thereon with the threaded stem of the spark plug and, of course, the grooves in the spark plug stem are of corresponding lengths to the electrode legs so that it is an easy matter to insert a new negative electrode on a spark plug body for Vthe replacement of a burned or worn one.

In the form of the invention illustrated in Fig. ures 1 to 4, the oating tip 23 of the center electrode moves between the adjacent open end of the fixed tubular section 22 of the center electrode and the center hump 29 on the cross arm of the 'f 5 U-shaped negative electrode in a chamber in the lower end of the porcelain I and moves into sealing contact with the open lower end of the center electrode section 22 on the compression stroke of an engine piston.

In the form of the invention illustrated in Figures 5 and 6, the porcelain I5 below the lower terminal end of the fixed tubular section 22 of the center electrode is provided with an annular chamber 32 denning a shoulder 33 and the floating tip 23a is of a diameter for abutting contact with the shoulder 33 and adjacent lower open end of the xed tubular electrode section 22 to form a double seal for a gas chamber and to reduce hammering action of the floating tip on the fixed tubular electrode section 22.

Another form of oating tip is shown in Figure '7 wherein the lower end of the porcelain I5 is provided with an enlarged annular chamber 32 in which the floating tip 231 is movable for contact at its upper end with the shoulder 33. The lower end of the fixed tubular electrode section 22 terminates upwardly of the shoulder 33 and the floating tip 23b carries a pin extension 34 working in the bore in the porcelain that houses the tubular electrode section and the upper end of this extension pin 34 is of a length to contact and seat on the lower open end of the xed tubular electrode section 22 when the upper end of the floating tip 23b contacts the shoulder 33,

thereby providing spaced points of sealing contact betewen the floating tip, porcelain I5, and the tubular section of the center electrode.

A modification of the U-shaped negative electrode I9 is illustrated in Figures 8 to 10 wherein the side grooves 2lia in the threaded stem I'I of the spark plug extend the complete length of the stem and terminate in sockets 35 in the shoulder 2l of the body I6. The negative electrode comprises unthreaded elongated legs 36 connected by a cross arm 31 and these legs are received at their free ends in sockets 35, and such legs are of a diameter with respect to the threads of the stem II as to present their outer sides slightly outwardly of the valleys of the threads. In mounting the spark plug shown in Figure 8 into a threaded port in the cylinder wall 38, as shown in Figure 10, the usual gasket 39 is interposed between the shoulder 2I of the spark plug body I6 and the cylinder wall 38 to be compressed thereby as illustrated and the threads of the cylinder wall port intimately contact the outer sides of the legs 36 to establish direct heat conductivity between the legs of the negative electrode cylinder wall and adjacent water jacket, and with a negative electrode of such character the major portion thereof is in contact with a cylinder wall for the dissipation of heat.

As illustrated in Figure 1l, the negative electrode is of the same general construction as the one illustrated in Figures 8 to 10, with the addltion of outwardly directed arm extensions 40 seated in grooves 4I in the shoulder 2I of the spark plug body I8 and covered by the usual gasket 39. The foregoing construction provides additional material forming a part of the negative electrode for the dissipation of heat from the negative electrode and through the gasket 39 to the shoulder wall and associated water jacket.

While there are herein shown and described the preferred embodiments of the invention, it is nevertheless to be understood that minor changes may be made therein without departing from the spirit and scope of the invention as claimed.

I claim:

1. A spark plug including an insulator and an enclosing body having diametrically opposite longitudinally extending grooves in the outer side of the threaded stem portion thereof, a U-shaped negative electrode having its legs removably tted in said grooves with the cross portion thereof extending across the outer end of said stem portion and a center positive electrode comprising a fixed tubular section anchored in the insulator and terminating upwardly of the lower end of the insulator, the lower end of the insulator having an enlarged annular chamber below the fixed electrode section defining an upper shoulder, and a floating tip movable between the fixed section and the cross portion of the U-shaped negative electrode and'said legs being dimensioned with respect to said grooves to produce a press and binding t in said grooves and to have contact with the threads of a ported opening in an engine cylinder wall to provide a good electrical as well as heat transfer contact for said negative electrode in operation, the lower end of the enclosing body having an annular shoulder at the upper end of the threaded stem with diametrically opposite radial grooves in the shoulder communicating at their inner ends with the grooves in said stem portion and terminating at their outer ends in proximity of the outer edges of the shoulder to form relatively long seats, an outwardly directed arm on the end of each side leg of the negative electrode seated in an adjacent shoulder groove and occupying the entire length thereof whereby contact of said legs and arm with a gasket interposed between the body shoulder and cylinder wall of an engine will increase h'eat transfer from the negative electrode to the cooling system of the' engine.

2. In a replaceable negative electrode for spark plugs wherein the lower end of the enclosing body of said plug has an annular shoulder at the upper end of a threaded stem and a pair of diametrically opposite radial grooves in said shoulder communicating at their inner ends with a pair of diametrically opposite longitudinally extending grooves in the outer side of said threaded stem, and with the grooves terminating at their outer ends adjacent the outer edge of the shoulder, the improvement consisting of a generally U-shaped electrode element provided with an outwardly directed arm on the end of each side leg adapted to seat in an adjacent shoulder groove and occupy the full length thereof whereby contact of said legs and arms with a gasket interposed between the plug shoulder and cylinder wall of an engine will increase heat transfer from the negative electrode to the cooling system of the engine.

LLOYD M. FIELD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,247,102 Forbes Nov. 20, 1917 1,464,685 Sundberg Aug. 14, 1923 2,371,162" Field Mar. 13, 1945 2,488,972 Field Nov. 22, 1949 FOREIGN PATENTS Number Country Date 502,690 France May 22, 1920 168,019 Great Britain Oct. 22, 1920 554,348 France June 8, 1923 

